Hitchcocks Forum

Does anybody know how firm the valve springs should be on a 1939 sidevalve 350 should be. Being able to open the valves with my finger just doesn't seem right lol

I should have added that this motor was in a fire hot enough to melt the half tappet door off

Hi Norm, I have one here. It's an engine which I stripped after it has lain outdoors for about 50 years, but the cylinder barrel seems quite good and has the valves and springs still in place. I will give the valve springs a press and report back later. Cheers, Paul.

Thanks Paul, this motor will not be going in a bike, it just has to end up as a running display engine, give it a start, let it choof away for a short time and everybody will be happy

Hi Norm, just checked and there are single springs in this one and with the barrel upturned, I can open the valves about 1/2" or so with thumb pressure, so yours might be ok. One thing, the valves are never going to hit the piston ! Cheers, Paul.

I would ask Guy Martin.



He did an excellent demonstration on finding tyre pressures by how much he could squeeze them!



We are not worthy...We are not worthy!

Thanks Paul, sounds about right, I guess gravity helps them shut and as the piston comes up the compression will help shut them. lol. Thanks again

Boy this motor had been hot, no oil in the pumps just crumble/carbon, and on the crank pin and conrod you could see where all the rollers had been sitting, quite amazing

Scalyback with reference to Guy Martin and tyre pressures. I suspect very few people could understand the frustration, anger, and outbursts of tears I have due to in the last few years losing my engineering "touch" with my fingers.
My father, (who had made wooden parts for Mosquito fighter bombers,) could never understand how I from a very young age could measure things accurately by eye and touch without the benefit of measuring tools.

My cobber is rebuilding a 16H Norton at the moment and it doesn't seem to particularly powerful valve springs. It's only about 5:1 compression too. Amazing that they go so well.